This invention relates to a novel support insulator for flexible gas-insulated transmission line cable, and more particularly relates to a novel support insulator which consists of three identical pie-shaped segments which snap together around the outer diameter of the central cable.
Flexible gas-insulated transmission line cable is well known in the art and examples of such cable and of support insulators therefor are shown in the above related applications and are also shown in U.S. Pat. No. 3,789,129, in the name of Ditscheid, and 3,996,414, in the name of Artbauer et al.
Support insulators for flexible cable have been made of two identical halves where each of the halves has two spring-like members extending from its outer rim in order to provide a pressure fit within the enclosure housing after the housing has been corrugated. In order to form these spring members, however, it has been necessary to break the outer rim surface. This break in the outer rim tends to reduce the creepage path between the central conductor and its outer grounded enclosure and thus increases the possibility of a flash-over in this area.
A further problem with the two-piece type insulator is that each of the identical parts are relatively large members formed by an injection-molding process. Since the parts are large, shrinkage during the molding process is not always completely uniform so that the resulting molded product is distorted from its desired shape. Thus, the part tends to shrink more across its outer diametral or end surface dimension than in any other radial dimension. Consequently, the center rim of the insulator half which fits around the central conductor of the transmission line cable is narrower across the break line or outer surface than at some distance, say 90.degree., from the mating surfaces of the two insulator halves. At the same time, the conductor sheath of the central conductor may be out-of-round so that, in some cases, it is not possible to assemble the insulator halves on the conductor.